View Full Version : New physics question
This question is about perception of speed.
If you are sitting still, not moving in any direction, and are passed by a car going 100 mph; will it look the same as if you are traveling in a car going 100 mph, and get passed by a car going 200 mph? So will there be any difference in the distance put between you over a fixed amount of time, between the two scenarios?
In both scenarios, the passing car is traveling 100 mph faster than the perspective point (you). There is only one difference as far as I can tell. When you are sitting still, for every 1ft the passing car travels away from you, you don't move. When you are driving 100mph, and are passed by the car moving 200 mph, for every 2 ft the passing car travels, you make up 1 of those feet.
I haven't put much thought into this one, but I suspect that it can be solved in 2 minutes with a simple distance traveled over time equation. I am no good at math, so I can't come up with said equation.
Have fun.
And if you really want to get involved, you'd throw this bumper sticker in there some where. [Beer]
http://blog.makezine.com/archive/2009/12/03/blueshiftbumpersticker.jpg
This question is about perception of speed.
If you are sitting still, not moving in any direction, and are passed by a car going 100 mph; will it look the same as if you are traveling in a car going 100 mph, and get passed by a car going 200 mph? So will there be any difference in the distance put between you over a fixed amount of time, between the two scenarios?
In both scenarios, the passing car is traveling 100 mph faster than the perspective point (you). There is only one difference as far as I can tell. When you are sitting still, for every 1ft the passing car travels away from you, you don't move. When you are driving 100mph, and are passed by the car moving 200 mph, for every 2 ft the passing car travels, you make up 1 of those feet.
I haven't put much thought into this one, but I suspect that it can be solved in 2 minutes with a simple distance traveled over time equation. I am no good at math, so I can't come up with said equation.
Have fun.
For the car, first off the background behind the vehicle you are looking at would be going by 100 MPH, while the car went by at +100 over your speed, so the look would be different. the first scenario everything would be sitting still except the car, the second scenario the background behind the car would be passing at 100 mph, but the look of the car itself would not really change because there is still a +100 MPH difference.
call it an hour. you are sitting still the car would be 100 miles away from you. second scenario, the car is still doing +100 MPH better than your car and would be 100 miles ahead of you in an hours time, but that car would be 200 miles away from the initial starting point when you first saw the vehicle and you would be 100 miles away from that point.
I've driven 200+mph.
my top is 136mph in a car (my first car, volkswagon passat with the 1.8T), 142mph on a crotch rocket(yamaha R1), and 695mph in a jet (groundspeed)
Yeah, that's pretty much how I break it down too.
I tried not to use the line, "Would it look the same" because it is so subjective. I guess you could describe the set-up in some really long tunnel or something. Either way, whether the perception of the car pulling away from you will look the same or not, the math shows that it should still pull away at the same speed given the variables.
Where at Mtn.Man? If it was in the quarter mile, isn't that like sub 7 second pass?
Motorcycle? circle track?
I pegged my Powerstrokes speedometer for 10 minutes,,no idea how fast.Never got pulled over either. Speedometer tops out at 120mph.
Where at Mtn.Man? If it was in the quarter mile, isn't that like sub 7 second pass?
Motorcycle? circle track?
Bandimere RED 201.96 6.96 sec.
37 Chevy P/M 207.37 6.78 sec
Pistol Packing Preacher
12-10-2009, 14:04
http://blog.makezine.com/archive/2009/12/03/blueshiftbumpersticker.jpg[/quote]
[ROFL1][ROFL3][LOL]
MPH is miles per hour, distance over time. The difference between 0 and 100 is 100. The difference between 200 and 100 is still 100. 100 Miles per hour (distance over time) not an abstract physics concept. There is no difference between the two objects in question in terms of distance/time between each other. They also no doubt both have blue/red lights distantly trailing the 200mph car.
Only difference would be the scenery moving for the latter.
And as I'm sure this will be asked next based on your other posts. I'll quote it out so I don't bore everybody, but this is one of the biggest physics issues i've seen firearm owners grapple with:
you failed to mention the skill it takes for me to be a space shuttle door gunner[Beer]
This dog perfectly demonstrates Foxtrots point:
http://i148.photobucket.com/albums/s10/jdean23_photos/Funny/doggyfailure.gif
This also helps with the explanation:
http://i148.photobucket.com/albums/s10/jdean23_photos/Funny/McDonaldgetsowned.gif
This chick did not do very well with the treadmill question. she forgot her ass doesn't produce that much thrust.
http://i148.photobucket.com/albums/s10/jdean23_photos/Funny/funny-1.gif
The new physics question:
http://i148.photobucket.com/albums/s10/jdean23_photos/Funny/Helo--willitfly.jpg
FoxTrot is all over this stuff... Good job Sir.
Sniper7,... Great pixs! HAHAHA.
What Foxtrot said is the reason I never spent much time thinking about this question. The math shows without a doubt what WILL happen, and from there it becomes a mental exercise of being able to picture it in your minds eye, and convince yourself that the receding vehicle will still appear to recede just as fast, even though now you are moving in the same direction at 50% of its speed, compared to 0% of its speed the first time.
I mean, what Foxtrot already said.
As far as the helicopter one, I thought people were just joking at first. I don't think I know enough about helicopters to get a solid answer on that one. Not to mention I haven't heard any specifics of the scenario. Anyone have more info?
ronaldrwl
12-11-2009, 19:49
Yes, it will look the same since speed is relative and you are never sitting still anyways.
so if you are driving 65mph and there is a fly in the back of your vehicle, and he flies from there to the front window ...How fast is he going?
two shoes
12-11-2009, 20:40
As far as the helicopter one, I thought people were just joking at first. I don't think I know enough about helicopters to get a solid answer on that one. Not to mention I haven't heard any specifics of the scenario. Anyone have more info?
Would depend on the direction/rotation of the blades and direction of the turntable relative to the air around it....
two shoes
12-11-2009, 20:45
so if you are driving 65mph and there is a fly in the back of your vehicle, and he flies from there to the front window ...How fast is he going?
A smart fly would use the boundary layer close to the vehicle's skin to fly through, His forward velocity relative to the ground would be in fact greater than 65 mph, but he would not have to over come the direct impingement of the wind while in said boundary layer... Just a thought
two shoes
12-11-2009, 20:47
A smart fly would use the boundary layer close to the vehicle's skin to fly through, His forward velocity relative to the ground would be in fact greater than 65 mph, but he would not have to over come the direct impingement of the wind while in said boundary layer... Just a thought
You meant inside the car.... shit I am still not a rocket scientist...
so if you are driving 65mph and there is a fly in the back of your vehicle, and he flies from there to the front window ...How fast is he going?
He would actually have a couple speeds. he would have 65mph + his forward airspeed, call it 5 mph. relative to the earth he would be doing 70mph. relative to the car, he would be doing 5 mph.
his airspeed would read 5mph if he were an airplane unless he went out the window, he would instantly receive a 65mph headwind and being doing 70mph but would quickly slow because of the drag on him, plus not having the required amount of thrust/power/wingspeed in order to maintain that speed.
two shoes
12-11-2009, 20:57
You meant inside the car.... shit I am still not a rocket scientist...
Some things still apply though....His speed relative to a fixed point on the ground would be greater than 65, but the fly does not have to overcome the wind resistance outside....
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